First Guess: Not the filter.
Second Guess: Leaking above the filter, drooling down onto the filter where it becomes noticeable. I'd be looking for a cracked filter adapter; possibly a gouge or divot on the gasket surface where the oil filter gasket seals to the adapter. A leaking adapter-to-engine gasket is another possibility.
Blow some talcum powder on everything in the area, see where it's wet. Or use ultraviolet dye in the oil and a UV lamp.